Arrangement for joining outer ring and shaft of homokinetic joint

ABSTRACT

There is provided an arrangement for mechanically and reliably joining a shell-type outer ring of a homokinetic joint and its shaft. A circular hole (4) is formed in a press formed end wall of an outer ring (1). A polygonal surface or serrated grooves are formed on the inner periphery of the hole (4). A protrusion (7) provided at one end of a shaft (5) is press-fitted in the hole (4) to join the outer ring and the shaft so that they will not rotate relative to each other. A caulking tool is used to deform protrusion (7) to form caulked portion (14) so that the outer ring (1) is prevented from moving axially relative to shaft (5).

TECHNICAL FIELD

This invention relates to an arrangement for joining an outer ring of ahomokinetic joint to its shaft.

BACKGROUND ART

Shell type outer ring, which can be formed by pressing, have beengaining attention because they are lightweight and can be manufacturedinexsensively.

But since a shell-type outer ring is formed from a thin steel plate, itis difficult to rigidly join with a shaft. A weak joint between theouter ring and the shaft could markedly lower the performance of thehomokinetic joint.

Unexamined Japanese Patent Publication 58-8831 proposes to join ashell-type outer ring to a shaft by means of bolts or by welding.

But bolting or welding reqiures a step in addition to forming an outerring by pressing. Since such a completely different manufacturing stepmust to be carried out in a single manufacturing line, workability tendsto be low.

Moreover, in the welding method, the strength of the outer ring tends todrop at its joint due to the influence of welding heat. Also, insituations where welding is not uniform; a high loading torque may breakthe joint portion between the outer ring and the shaft.

An object of this invention is to provide an arrangement for joining theouter ring of a homokinetic joint to its shaft with high reliability,not by welding, but by a simple mechanical means.

According to this invention, there is provided an arrangement forjoining an outer ring to a shaft of a homokinetic joint. The arrangementis comprised of a hole formed in the outer ring to receive the shaft,the hole being formed by pressing. The hole, in turn, has a plurality offlat surfaces or grooves. One end of the shaft is then press-fitted intothe hole to join the outer ring to the shaft.

Preferably, the inner surface of the hole is harder than the engagingportion at one end of the shaft.

Since the outer ring and the shaft are prevented from turning relativeto each other by the flat surfaces or serrated grooves formed on theinner periphery of the hole of the outer ring in which the shaft ispress-fitted, the outer ring and the shaft can be coupled together withhigh reliability.

Since the surface of the hole formed in the outer ring is harder thanthe portion of the shaft inserted into the hole, the shaft can be heldstably in position once it is press-fitted in the hole, with the portionof the shaft fitted in the hole deformed so as to conform to the shapeof the hole.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a sectional view of a first embodiment of the inventionshowing an outer ring being joined to a shaft;

FIG. 1B is a sectional view of the outer ring and shaft of FIG. 1A afterjoining;

FIG. 2A is a front view of the outer ring of the first embodiment;

FIG. 2B is a front view of the end of the shaft;

FIG. 3A is a front view of an outer ring of a second embodiment;

FIG. 3B is a front view of the end of the shaft of FIG. 3A;

FIG. 4A is a sectional view of a third embodiment of the inventionshowing an outer ring being joined to a shaft; and

FIG. 4B is a sectional view of the outer ring and shaft of FIG. 4A afterjoining.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of this invention will now be described with referenceto the drawings.

As shown in FIGS. 1 and 2, an outer ring 1 is a cup-shaped member formedby pressing a thin-walled steel pipe or a cylindrical material having aclosed bottom. A plurality of track grooves 2 are formed in the innerperiphery of the outer ring 1 so that the outer ring has a petal-shapedcross-section. A homokinetic joint is assembled by mounting a torquetransmission member 3 comprising balls, a cage and an inner ring in theouter ring 1. The outer ring 1 has a hole 4 formed in the center of itsend wall la by punching.

The hole 4 has a polygonal surface 8 as shown in FIG. 2A or a serratedsurface 10 as shown in FIG. 3A. The surface 8 or 10 is hardened bycarburizing or induction hardening.

A shaft 5 has a large-diameter portion 11 at one end and a protrusion 7formed at the end of the large-diameter portion 11 and with theprotression 7 being inserted into the hole 4 of the outer ring 1.Threads 6 are formed on the outer periphery of the shaft 5 at the otherend thereof.

The surface of the protrusion 7 is not hardened. Its diameter isslightly larger than that of the hole 4. A seal 12 is fitted in a groove13 formed in a shoulder between the protrusion 7 and the large-diameterportion 11.

The shaft 5 is joined to the outer ring 1 by press-fitting theprotrusion 7 of the shaft 5 into the hole 4 of the outer ring 1 as shownin FIG. 1A, and striking the end of the protrusion 7 protruding into theouter ring 1 in the axial direction with a caulking tool 9 to form acaulked portion 14 at the end of the shaft 5, as shown in FIG. 1B.

By press-fitting and caulking, the polygonal shape of the surface 8 andthe serration of the surface 10 are transferred to the projection 7, sothat the outer ring 1 is prevented from rotating. By caulking, the shaft5 is joined to the outer ring 1 without any axial play therebetween. Theouter ring 1 will rotate together with the shaft 5. Caulking the end ofthe projection 7 has an additional effect of correcting any deformationof the end wall la of the outer ring 1 that may occur upon press-fittingthe shaft 5 into the hole 4.

FIGS. 4A and 4B show the second embodiment, in which a shaft 5,including a threaded portion 6 at one end thereof, is slightly smallerin diameter than the hole 4 of the outer ring 1, except that an engagingportion 15 at the other end of the shaft 5, is slightly larger indiameter than the hole 4. The engaging portion 15 is provided with aflange 16 at its extreme end that prevents separation of the shaft andthe outer ring. The hole 4 of the outer ring 1 has a polygonal surface 8or serrated surface 10 similar to those shown in FIGS. 2 and 3 and issubjected to hardening.

The shaft 5 is inserted into the hole 4 from inside the outer ring 1 asshown by the arrow in FIG. 4A, until the engaging portion 15 abuts a die17. In this state, the shaft 5 is struck with a caulking tool 9 as shownin FIG. 4B to form a caulked portion 18 thereby constituting a flangemember. The portion of the engaging portion 15 fitted in the hole 4 isdeformed into the polygonal or serrated shape conforming to the shape ofthe polygonal surface 8 or serrated surface 10.

Industrial Application

According to this invention, as fully described above, the outer ringand the shaft are mechanically joined together by pressing. Thus, themanufacturing steps of press-forming the outer ring and joining theouter ring to the shaft can be carried out continuously, so thathomokinetic joints can be manufactured with high efficiency.

Since the outer ring and the shaft are prevented from rotating relativeto each other by the flat surfaces or serrated grooves formed on theinner periphery of the hole of the outer ring in which the shaft ispress-fitted, the outer ring and the shaft can be coupled together withhigh reliability. The homokinetic joint thus formed will operate stably.

Since the surface of the hole formed in the outer ring is harder thanthe portion of the shaft inserted into the hole, the shaft can be heldstably in position once it is press-fitted and deformed into the shapeof the hole. The outer ring and the shaft can thus be strongly joined.

We claim:
 1. A homokinetic joint arrangement comprising:an outer ringhaving a hole, said hole having a noncircular inner peripheral surface;a shaft having a solid protrusion at one end-thereof; wherein saidprotrusion is sized such that the diameter of an imaginary circleinscribed in said hole is smaller than the diameter of an imaginarycircle circumscribed about said protrusion, such that said protrusion ispress-fitted within said hole.
 2. The homokinetic joint arrangement ofclaim 1, wherein said noncircular inner peripheral surface is formedwith a plurality of flat faces.
 3. The homokinetic joint arrangement ofclaim 1, wherein said noncircular inner peripheral surface is formedwith a plurality of grooves.
 4. The homokinetic joint arrangement ofclaim 1, wherein said noncircular inner peripheral surface is harderthan said protrusion.
 5. The homokinetic joint arrangement of claim 1,wherein said shaft further comprises a large diameter portion having adiameter greater than the diameter of said protrusion, said shaftfurther having a flange portion having a diameter greater than thediameter of said protrusion, whereby said outer ring is sandwichedbetween said large diameter portion and said flange portion.
 6. Thehomokinetic joint arrangement of claim 1, wherein said outer ring iscup-shaped.
 7. A homokinetic joint arrangement comprising:an outer ringhaving a hole, said hole having a noncircular inner peripheral surfaceformed with a plurality of flat faces; a shaft having a protrusion atone end thereof, said protrusion having a flange portion with a diametergreater then the diameter of said protrusion, said shaft also having alarge diameter portion having a diameter greater than the diameter ofsaid protrusion; wherein said protrusion is sized such that the diameterof an imaginary circle inscribed in said hole is smaller than thediameter of an imaginary circle circumscribed about said protrusion, sothat said protrusion is press-fitted within said hole, and that saidouter ring is sandwiched between said large diameter portion and saidflange portion.
 8. The homokinetic joint arrangement of claim 7, whereinsaid noncircular inner peripheral surface is formed with a plurality ofgrooves.
 9. The homokinetic joint arrangement of claim 7, wherein saidnoncircular inner peripheral surface is harder than said protrusion. 10.The homokinetic joint arrangement of claim 7, wherein said outer ring iscup-shaped.
 11. A homokinetic joint arrangement comprising:an outer ringhaving a hole, said hole having a noncircular inner peripheral surface;a shaft having a protrusion at one end thereof, said protrusion having aflange portion with a diameter greater then the diameter of saidprotrusion, said shaft also having a large diameter portion having adiameter greater than the diameter of said protrusion; wherein saidnoncircular inner peripheral surface is harder than said protrusion; andwherein said protrusion is sized such that the diameter of an imaginarycircle inscribed in said hole is smaller than the diameter of animaginary circle circumscribed about said protrusion, so that saidprotrusion is press-fitted within said hole, and that said outer ring issandwiched between said large diameter portion and said flange portion.12. The homokinetic joint arrangement of claim 11, wherein saidnoncircular inner peripheral surface is formed with a plurality ofgrooves.
 13. The homokinetic joint arrangement of claim 11, wherein saidouter ring is cup-shaped.